Control switch



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IN VEN TOR. STEPHEN CRUM ATTORNEY S. CRUM CONTROL SWITCH May 13, 1952 2SHEETS-SHEET 2 Filed Dec. 10, 1949 INVENTOR. STEPHEN CRUM ATTORNEYPatented May 13, 1952 7 UNITED STATES PATENT OFFICE CONTROL I SWITCHStephen Crum, Minneapolis, Minn., assignor, to Minneapolis-HoneywellRegulator Company, Minneapolis, Minn., a corporation of DelawareApplication December 10, 1949, Serial No. 132,255

10 Claims. (01. zoos-139) This invention relates to condition responsivecontrol devices and more particularly to such devices in which a singlecondition responsive element actuates more than one control element.

An object of the invention is to provide a control device in which acondition responsive element actuates one control element at onecondition value and another control element at a condition value that isadjustable.

Another object is to provide a control device in which a singlethermostatic element actuates one switch at an adjustable temperatureand another switch at a normally fixed temperature.

Another object is to provide a thermostat in which two switches areactuated at independently adjustable temperatures.

Otherobjects will be apparent from the following written description andclaims, and from the drawing, in which Figure 1 is a front elevation ofa thermostat embodying the various features of the invention, the coverhaving been removed,

Figure 2 is a side elevation, partly in section, of the device shown inFigure 1 as seen from the right,

Figure 3 is a view similar to Figure 1 but with the mercury switches andtheir lead wires removed, and

Figure 4 is a fragmentary view showing the switch actuating linkage inthe position it assumes to actuate the lower mercury switch.

The illustrative embodiment of the invention is a combination furnacefan and high limit control for use with forced warm air furnaces. Asingle bimetal element actuates both the fan switch and the limitswitch. In what probably is the most common electrical wiringarrangement the fan switch causes operation of the blower only at bonnettemperatures sufiiciently high so that the discharged air will not beuncomfortably cool. The fan switch is adjustable from outside the casingso that it may be set to make contact at the furnace bonnet temperatureindicated on the scale. The limit switch is provided with a factoryadjustment to determine the furnace temperature at which it will breakcontact to shut down the burner. The arrangement is such that the fanswitch setting may be adjusted without affecting the limit switchsetting. The fan switch control point is set by a conventional back endadjustment, and a novel linkage is provided whereby the limit switchcontrol point is unaffected by such adjustment of the fan switch.

A base I is provided with a pair of lower 2 V mounting holes II and anupper mounting hole I2 in its back surface to facilitate mounting thedevice on the bonnet of a warm air furnace. .A sleeve [3 secured to theback of the base I0 is adapted to extend within the bonnet of thefurnace and is provided with a plurality of openings M to provide accessof the air within the furnace to a helical bimetal element l5. A tube l6which is journaled in th base ID at I! and in the tube 13 at I8 carriesthe inner end of the bimetal element I5. A rod [9 which is journaled inthe tube at 20 carries the outer end of the bimetal element.

A generally cup-shaped member 22 is staked to the inner end of the tubeI6 and is provided with a central aperture through which therod [3extends. The periphery of the member 22 engages the inner surface ofbase [0. An adjusting member 23 overlies cup-shaped member 22 and isprovided with an aperture concentric with the aperture in member 22. Themember 23 is provided with an arcuate slot 24 which receives a screw 25,the arrangement being such that a limited amount of pivotal adjustmentis permitted between the members 22 and 23. A bushing 26 is locatedwithin the aperture in the member 23 and is provided with a centralopening that serves as a bearing for the inner end of the rod IS. Aspring plate 2! overlies the bushing 26 and has its end secured by theedges of the base I0. The plat 21 provides a bias on thebushing 26 whichholds the members 22 and 23 and the tube IS in place within thesleevel3.v The plate 21 also provides a frictional drag to maintain the tubeIS in its adjusted position. The arrangement is such that the tube I6and the rod 13 are coaxially pivoted in the base It).

A mercury switch 33 is mounted in a clip 3| which is carried by abracket 32. The bracket 32 is staked to a collar 33 carried by the innerend of rod IS. The mercury switch 30 is connected by a pair of flexiblelead wires 36 and 31 to terminals 38 and 39 secured to an insulatingterminal strip 43 which is carried by the base ID. The lower end of themember 23 carries a pointer 42 which cooperates with suitable indicia oftemperature on a scale plate 43. The relation between the tube l6 andthe pointer 42 is adjusted by means of the screw and slot 24 in thmembers 22 and 23 so that the mercury switch will be actuated to onposition when the bimetal element 15 reaches the temperature indicatedon the scale plate 43.

An adjusting arm 45 is carried by the collar 3? and is pivotallyadjustable about the collar 33 to various angular relations with respectto the switch bracket 32. The axis of adjustment of the arm 45 is, ofcourse, the axis of the rod I 9. The left-hand end of the arm 45 carriesa screw 41 which extends through an arcuate slot 48 in an extension ofthe switch bracket 32. Tightening the screw 41 secures the arm 45 to thebracket 32 so they will move as a unit on changes in temperature of thebimetal element l5.

A pivot post 50 is carried by a. right-hand extension of the arm 45. Alever 52 has its righthand end pivoted, by means of a slot therein, onthe post 50. The left-hand end of the lever 52 is pivoted on a post 53thatis carried by an extension of the member 23. A second mercury switch55 is carried in a clip 56 which lspivotally adjustable with respect toa bracket 51 by means of an eccentric 58. Bracket 51 is pivotallymounted in the base ID on a pin 59 which is carried by a bracket 60securedt'o the "base iii. A link 62 interconnects a right-hand extensionof the bracket 51 and an intermediate portion of the lever 52. A pin 63carrie'd by the bracket 51 serves as the pivotal connection between thebracket 51 and the link 62, while a pin 64 pivotally connects the link62 and lever 52. The distance along the lever 52 between the pin 64 andthe post '53 is the same as the distance between the post '53 and theaxis of the rod is and tube Hence, under certain conditions the pivotalaxis of the link 62 in the lever 64 will be coinci dent with the axis ofthe rod l9.

A pair of'fiexlble conductors 51 and 68 con nect the mercury switch 55to a pair of terminals Stand 10 on'the terminal strip 40.

Themercuryswitch 55 is adjusted by means of the eccentric 58 so that itwill break contact when the axis of the pin 64 interconnecting the link62 and the lever 52 iscoincident with the axis of the rod I 9. This willoccur when the temperature of the bimetal element I is at a value'suchthat the post 50 is diametrically opposite the post 53 with respect tothe pivotal axis ofthe rod 19. This temperature may be varied, however,since the relation between the rod 19 and the post 50 is adjustable bymeans of the screw 41 and the slot 48.

It will be seen that when the axis of'the pin 64 interconnecting lever52 and link 62 is coincident with the axis of the rod 19 that adjustmentof the member 23 to adjustthe control point of the mercury switch '30will have no effect on the position of the mercury switch 55. Movementof the member 23 will move the post 53 but it will also move the tube 16a like amount and, through the bimetal element l5, will move the rod H!a like amount to shift the position of the post 50 the proper amount tomaintain the position of the pin 64. At other temperature valuesadjustment of the member 23 will cause some movement of the pin 64 andsome movement of the mercury switch 55, but all such positions of themercury switch 55 are "on positions and therefore have no effect on itscircuit controlling operation.

Adjustment of the temperature at which the mercury switch 55 will beoperated to open circuit position is accomplished during manufacture ofthe device by placing the bimetal element [5 in an oven adjusted to thetemperature at which it is desired to have the switch operate. In orderto facilitate such adjustment and to determine the point at which theaxis of the pin 64 is coincident with the axis of the rod [9, the

left-hand end of the lever 52 is provided with a pointer 13 whichcooperates with a pointer 14 on the adjusting arm 45. When thesepointers are in alignment, as shown in Figure 4, the screw 41 may betightened to secure the arm 45 in a position that will actuate themercury switch 55 when that temperature is reached. It may be convenientto make .this adjustment so that the switch 55 is actuated to opencircuit position at some temperature in the neighborhood of 200 F.

No adjustment is provided in this device for the temperatures at whichthe two mercury switches will be actuated to their opposite circuitcontrolling positions. Such temperature values may be determined byselecting mercury switches having the desired operating angles.

A suitable cover 16 is provided to enclose the switching mechanism. Thismay be secured in place on the base 10 by a bracket 11 and a screw 18.The scale plate 43 is provided with an armate slot to receive a screw 8|carried by the member 23. This screw may be tightened to secure themember 23 against unauthorized tampering.

Various other embodiments of the invention will be apparent to thoseskilled in the art. The

scope of the invention is to be determined, therefore, only by theappended claims.

I claim:

1. In a'control device, a'frameffirst and second members coaxiallypivoted in said frame, a condition responsive element operativelyconnected to each member for relatively positioning said members aboutsaid axis in accordance withcondition value, cooperating indicia ofcondition value on said first member and said frame, a first controlelement actuated by said second member at the condition value indicatedby saidlindicia, a lever pivotally connected to said first and secondmembers on'opposite sides of said-axis, and a second control elementactuated by an inter mediate portion of said leverat a condition valuesuch that the pivotal connections of said link to said members arediametrically opposed with respect to said axis.

2. In a control device, a frame, first and second members coaxiallypivoted in said frame on a first axis, a helical bimetal elementoperatively connected to each member for relatively positioning saidmembers about said axis in accordance with temperature, means foradjustably positionin said first member in said frame, a first switchactuated by said second member at a temperature depending on theadjusted position of said first member in said frame, a lever pivotallyconnected at opposite ends to said first and second members on axesparallel to said first axis but disposed on opposite sides thereof, anda second switch actuated by an intermediate portion of said lever.

3. In a control device, a frame, first and second members coaxiallypivoted in said frame on a first axis, a helical bimetal elementoperatively connected to each member for relatively positioning saidmembers about said axis in accordance with temperature, means foradjustably positioning said first memberin said frame, a first switchactuated by said second member at a temperature depending on theadjusted position of said first member in said frame, a lever pivotallyconnected at opposite ends'to said first and second'members on axesparallel to'said first axis but disposed on opposite sides thereof, asecond switch, means operatively connecting said second switch and apoint on said lever in line with said first axis at the temperature atwhich the pivotal axes of said lever in said members are diametricallyopposed with respect to said first axis.

4. In a control device, a frame, a sleeve pivoted in said frame, a rodpivoted in said sleeve, a helical bimetal element interconnecting saidrod and said sleeve for rotating said rod relative to said sleeve onchanges in temperature, a mercury switch carried by said rod, a firstmember rotatable with said sleeve, a second member rotatable with saidrod, cooperating indicia of temperature on said frame and said firstmember for indicating the temperature at which said mercury switch isactuated, a second mercury switch pivoted in said frame, a leverpivotally connected to said first and second members, and a linkpivotally connected at one end to said lever at a point intermediate itsconnections to said members and at the other end to said second mercuryswitch, the arrangement being such that said second switch is actuatedwhen the connection between said lever and said link is substantially inline with the pivotal axis of said rod and hence at a temperatureindependent of the adjusted position of said member in said frame.

5. In a control device, a frame, first and second members coaxiallypivoted in said frame, a thermostatic element interconnecting saidmembers and adapted to relatively position said members about said axis,means for pivotally adjusting said first member in said frame, a firstswitch actuated by said second member at a temperature determined by theadjusted position of said first member in said frame, a lever pivotallyconnected at opposite ends to said first and second members at points onopposite sides of the pivotal axis of said members in said frame, asecond switch and means interconnecting said second switch and a pointon said lever which, at a predetermined temperature of said element,lies on the axis of said members, said interconnecting means beingadapted to actuate said second switch at said predetermined temperature.

6. In a control device, a frame, first and second members coaxiallypivoted in said frame on a first axis, a thermostatic elementinterconnecting said members adapted to relatively position said membersabout said axis, a first switch actuated by said second member at atemperature depending on the position of said first member in saidframe, a second switch, and a lever pivotally connected at one point tosaid first member on an axis displaced from said first axis, pivotallyconnected at a second point to said second member on an axis displacedfrom said first axis and at a third point to said second switch on anaxis that is in line with said first axis at a predeterminedtemperature, at which temperature said second switch is actuated.

7. In a control device, a frame, first and second members coaxiallypivoted in said frame, a conditionresponsive elementinterconnectingsaidmembers adapted to position said second member with respect to saidfirst member in accordance with condition value, a first switch actuatedby said second member at a condition value depending on the position ofsaid first member in said frame, a lever, connections between spacedpoints on said lever and said members, a second switch, and

a connection between said second switch and a point on said lever thatis stationary for all adjusted positions of said first member in saidframe at a predetermined condition value, said second switch beingactuated at said predetermined condition value.

8. In a control device, a frame, a tube and a rod coaxially pivoted insaid frame, a thermostatic element interconnecting said rod and saidtube adapted to angularly position said rod with respect to said tube inaccordance with temperature, a first switch actuated by said rod at atemperature depending on the position of said tube in said frame, afirst member attached to said tube and rotatable therewith, a secondmember carried by said rod, means for adjusting the angular relationbetween said second member and said rod, a lever pivotally connected atopposite ends to said first and second members at points on oppositesides of the pivotal axis of said tube and rod in said frame, a secondswitch, and an actuator for said second switch pivotally connected tosaid lever on an axis that lies on the pivotal axis of said tube and rodat a temperature determined by the adjusted angular relation betweensaid second member and said rod.

9. In a control device, a frame, a tube and a rod coaxially pivoted insaid frame, a thermostatic element interconnecting said rod and saidtube adapted to angularly position said rod with respect to said tubeilraccordance with temperature, a first member attached to said tube androtatable therewith, a second member attached to said rod and rotatabletherewith, a first switch actuated by said second member at atemperature depending on the position of said tube in said frame, athird member positioned by said second member, means for adjusting saidthird member with respect to said second member about the axis of saidrod, a lever pivotally connected at opposite ends to said first andthird members on pivots on opposite sides of the axes of said tube andsaid rod, a second switch, and an actuator for said switch pivotallyconnected to said lever on an axis that lies on the axis of said tubeand said rod at a predetermined relative position of said first andthird members.

10. In a control device, a frame, first and second members coaxiallypivoted in said frame, a condition responsive element operativelyconnected to each member for relatively positioning said members aboutsaid axis in accordance with condition value, means for pivotallyadjusting said first member in said frame, a first control elementactuated by said second member, a lever pivotally connected at oppositeends to said first and second members on axes parallel to the first axisbut disposed on opposite sides thereof, and a second control elementactuated by an intermediate portion of said lever.

STEPHEN CRUM.

REFERENCES CITED UNITED STATES PATENTS Name Date Kronmiller June 14,1938 Number

